1. Technical Field
The present invention relates to aircraft electronics, and more particularly to an integrated modular avionics package that integrates a flight control module.
2. Background Information
Referring to FIG. 1, a typical airplane includes fuselage 110, which holds the passengers and the cargo; wings 112, which provide the lift needed to fly the airplane; vertical stabilizer 114 and horizontal stabilizers 116, which are used to ensure a stable flight; and engines 118, which provide the thrust needed to propel the airplane forward.
To guide an airplane, one must rely on flight control surfaces that are placed on wings 112, horizontal stabilizers 116, and vertical stabilizers 114. The primary flight control surfaces on an airplane include the ailerons 100, the elevators 102, and the rudder 104. Ailerons 100 are located on the trailing edges of the wings of the airplane and control the roll of the airplane. Rolling of an airplane is depicted in FIG. 2A. Elevators 102 are located on the horizontal stabilizer of an airplane and control the pitch of the airplane. Pitching of an airplane is depicted in FIG. 2B. Rudder 104 is located on the vertical stabilizer and controls the yaw of the airplane. Yawing of an airplane is illustrated in FIG. 2C.
Also present on the wings of an airplane are spoilers 106, flaps 120, and slats 122, collectively known as secondary flight control surfaces. Spoilers 106 are located on the wings and perform a variety of different functions, including assisting in the control of vertical flight path, acting as air brakes to control the forward speed of the airplane, and acting as ground spoilers to reduce wing lift to help maintain contact between the landing gear and the runway when braking.
Flaps 120 and slats 122 are located on the wings of an airplane to change the lift and drag forces effecting an airplane, with flaps 120 at the trailing edge of wing 112 and slats 122 at the leading edge of wing 112. When flaps 120 and slats 122 are extended the shape of the wing changes to provide more lift. With an increased lift, the airplane is able to fly at lower speeds, thus simplifying both the landing procedure and the take-off procedure.
The primary flight control surfaces described above are operated by a pilot located in the cockpit of the airplane. Rudder 104 is typically controlled by a pair of rudder pedals operated by the pilot""s feet. Ailerons 100 are controlled by adjusting a control stick to the left or right. Moving the control stick to the left typically controls the left aileron to rise and the right aileron to go down, causing the airplane to roll to the left. Elevator 102 is controlled by adjusting a control wheel or control stick to the front or back.
In most smaller airplanes, there is a direct mechanical linkage between the pilot""s controls and the moveable surfaces. In most larger airplanes, there may be cables or wires connecting the pilot""s controls to the hydraulic actuators used to move the primary control surfaces. In newer planes, a system called xe2x80x9cfly-by-wirexe2x80x9d has been developed.
In a typical, prior art, fly-by-wire airplane, electronic sensors are attached to the pilot""s controls. These sensors transmit electronic data to various flight control computers (xe2x80x9cFCCxe2x80x9d). A system known as the actuator control electronics (xe2x80x9cACExe2x80x9d) receives the electronic signals from the flight control computer and move hydraulic actuators based on the received signals. Each hydraulic actuator is coupled to a moveable primary control surface such that movement of the actuator moves the primary control surface.
The fly-by-wire concept results in a savings of weight as there is no longer a need for heavy linkages, cables, pulleys, and brackets running throughout the airplane to control the actuators, only electrical wiring to the FCC and the ACE. Furthermore, this concept may result in a smoother flight, with less effort needed by the pilot.
During aircraft operation, the pilot of the airplane may need certain pieces of data to assist in flying the airplane. This data includes air speed, altitude, weather, location, heading and other navigational data. The data is generated by sensors located in various parts of the aircraft. The systems used to generate and report this and other information management data is generally termed xe2x80x9cavionics.xe2x80x9d The term xe2x80x9cavionicsxe2x80x9d also encompasses auto-pilot functions, which allow a computer to make inputs to the pilot""s controls. In modern fly-by-wire airplanes, the avionics systems may be placed in a cabinet in order to share, for example, power supplies, processors, memory, operating systems, utility software, hardware, built-in test equipment, and input/output ports. This grouping of avionics is known in the art as integrated modular avionics (xe2x80x9cIMAxe2x80x9d).
The IMA gathers and process data for a number of functions, including, but not limited to, flight management, displays, navigation, central maintenance, airplane condition monitoring, flight deck communications, thrust management, digital flight data, engine data interface, automatic flight, automatic throttle, and data conversion.
The original concept behind the IMA was the elimination of the need for line replaceable units (LRU) for each subsystem, each with its own power supply, processor, chassis, operating system, utility software, input/output ports, and built-in test units. Each of these functions were shared by the IMA, resulting in a great weight savings.
In a typical fly-by-wire controlled airplane, the movements of the control stick must be translated into the appropriate electronic instructions that can be executed by the ACE. In the prior art, this translation was performed by the FCC. The prior art separated the FCC from the IMA and combined the FCC with the ACE.
When a new airplane is designed and built, and before it can be flown with passengers, it must be certified. In the United States, the Federal Aviation Regulations (xe2x80x9cFARxe2x80x9d) govern the certification of planes. The FAR regulates potential problems that may occur in an airplane and divides components into various categories depending on the criticality of the component. For example, a Category A component is a component that, if it fails, results in loss of aircraft. A Category A component is also known as a Critical component. A Category B component is a less important component: failure of a Category B component may result in the loss of life, but not the loss of the entire airplane. Components in Categories C, D, and E are even less critical: failure any of those components results in no loss of life.
Critical components can be broken up into full-time critical and part-time critical components. A component is considered full-time critical if it is critical (i.e., loss of airplane can result if the component fails) in every flight for the duration of each flight. A system is considered part-time critical if it is critical for only a short period of time during each flight. For example, stall protection is critical at low altitudes because stall protection lowers the nose of the airplane, which can result in the loss of the airplane at low altitude. However, stall protection at cruising altitude is not critical because lowering the pitch of the airplane at 31,000 feet is not inherently dangerous. A system is also considered part-time critical if the condition or system is critical but does not happen in every flight (for example, the loss of an engine).
For full-time critical components operated by software, xe2x80x9csimilar redundancyxe2x80x9d (also known as xe2x80x9cdesign diversityxe2x80x9d) is standard. In similar redundancy, two computing systems are employed in the airplane that are similar, but not identical, to each other. For example, two computing channels could be used, with each computing channel having a different CPU and different software. In the alternative, the same CPU might be used for each computing path, but different software (for example, developed by a separate group of programmers) would be used. The theory behind similar redundancy is that, if one of the computing lanes makes a mistake, it is unlikely that a second computing lane, performing the same function but in a different manner, would contain the same fault that occurs at the same place.
Such a similar redundancy scheme results in increased development costs, because the same software program must be developed twice. However, the FAR only require that full-time critical components have similar redundancy. There is no such requirement for part-time critical components.
The IMA of the prior art did not include an FCC, because some argue that the critical components and the non-critical components should not be placed in the same IMA housing or cabinet, to avoid having the failure of a non-critical component effect the availability of a critical component. Because the Flight Control Computer directly controlled the primary control surfaces, the Flight Control Computer was Critical in the prior art. Therefore, the prior art placed the Flight Control Computers in a separate module to ensure that the failure of the IMA would not result in the failure of the primary flight control surfaces.
There are several disadvantages to this approach. The first disadvantage is the added development cost because of the need for similar redundancy. The development costs for the software is almost doubled because the software must be developed twice. Furthermore, there is extra weight on the airplane because of the need for a separate Flight Control Computer with a separate power supply and separate processing capabilities. The separation of the FCC results in another disadvantage because of the way a typical FCC communicates with the IMA over a standard ARINC 629 bus. The ARINC 629 bus is slower than the bus internal to the IMA. Thus, for the IMA to transmit data to the FCC as it is being processed, either less data must be transmitted, or the same data must be transmitted over a longer period of time. Because of the importance of receiving information in a timely manner, prior art designers chose to transmit less data. Therefore, a separate FCC does not receive the full flight information generated by the IMA. What is needed is a system that alleviates or eliminates these problems.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can only be gained by taking the entire specification, claims, drawings, and abstract as a whole.
The present invention incorporates a flight control module into the avionics of an airplane. The flight control module is coupled to an actuator control electronics system which operates a hydraulic actuator coupled to a flight control surface. The flight control module provides augmentation information to the actuator control electronics system. However, in the actuator control electronics system is also capable of operating based solely from inputs provided by a pilot through a control stick, without any such augmentation from the flight control module in a xe2x80x9cdirect mode.xe2x80x9d
The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention or can be learned by practice of the present invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain embodiments of the present invention, are provided for illustration purposes only, because various changes and modifications within the spirit and scope of the invention will become apparent to those of skill in the art from the detailed description of the invention and claims that follow.